Video Converter – Convert Any Video to MP4, MOV, WebM or MKV
This free video converter turns MKV, MOV, AVI, WebM, WMV and other files into MP4, WebM, MOV or MKV inside your browser. When the video stream already fits the new format, ProMedia copies it instead of re-encoding, so the picture stays identical and the job takes seconds. Nothing is uploaded, there is no file-size cap and the output carries no watermark.
- Runs on your device
- WebCodecs · GPU
- FFmpeg
- Works offline
Updated
Drop your videos here
How to convert a video to MP4
Step 1: Drop one or more videos on the box above, or tap it to choose them. A mix of formats in one batch is fine.
Step 2: Under Convert to, keep MP4 for phones, TVs and editors, or pick WebM, MOV or MKV.
Step 3: Leave Quality on Balanced. It only matters for tracks that have to be re-encoded; codec, resolution and frame rate sit under Advanced settings.
Step 4: Press Convert. Each result card says whether the video was copied or re-encoded.
Step 5: Download the files one by one, or all of them as a ZIP.
Good to know
Settings explained
- Quality
- Only used when a stream has to be re-encoded. Compatible streams are copied with no quality loss.
- Faster: Smaller file, quickest export
- Balanced: Good quality at a sensible size
- Best quality: Largest file, slowest export
- Video codec
- Automatic copies the original video stream when the new format can hold it, so there is no quality loss.
- Automatic: Best codec the format and your device support
- H.264 (AVC): Plays everywhere
- H.265 (HEVC): About 35% smaller, newer devices
- VP9: Web / WebM
- AV1: Smallest files, slowest to encode
- Always re-encode
- Off: compatible streams are copied instantly and losslessly. On: every stream is re-encoded, which can fix playback glitches.
Formats
Batch-friendly: add many files and they are processed one after another — if one fails, the rest still finish.
How it runs
- Hardware video engine
- Video is decoded and encoded by your device’s media hardware through WebCodecs — usually several times faster than real time.
- FFmpeg (when needed)
- Older formats and a few filters use FFmpeg compiled to WebAssembly. It downloads once (about 31 MB) the first time it is needed and is cached for offline use.
MP4 vs WebM vs MOV vs MKV: which video format is best?
For sharing, MP4 with H.264 video and AAC audio is the safest choice: phones, browsers, TVs, chat apps and editors all play it. WebM suits web pages, MOV suits Apple editing apps and MKV is the most flexible box for archives. The table shows what each format holds when this converter writes it.
| Feature | MP4 | WebM | MOV | MKV |
|---|---|---|---|---|
| Video copied without re-encoding | H.264, HEVC, AV1, VP9, VP8 | VP9, VP8, AV1 | H.264, HEVC, AV1, VP9, VP8, ProRes | H.264, HEVC, AV1, VP9, VP8 |
| Audio copied without re-encoding | AAC, Opus | Opus, Vorbis | AAC, Opus | Any audio the file already has |
| Audio that has to be converted becomes | AAC | Opus | AAC | AAC |
| Video codec used when re-encoding | H.264 | VP9 (VP8 for AVI, WMV and other old formats) | H.264 | H.264 |
| Best for | Sharing, uploading, phones, TVs | Web pages and HTML5 players | iMovie, Final Cut, QuickTime | Archives, multi-language files |
Which formats can this video converter open?
Modern containers (MP4, M4V, MOV, MKV, WebM and MPEG-TS) are read by the browser itself through WebCodecs, which is what makes lossless copies fast. Older formats such as AVI, WMV, FLV and MPG go through FFmpeg compiled to WebAssembly, an engine of about 31 MB that downloads the first time it is needed and is then cached.
Every common source has its own page with settings tuned for it. They all run the same converter, so you can also stay here and choose the output yourself.
| Source format | Read by | Usual result | Dedicated page |
|---|---|---|---|
| MKV (Matroska) | Browser | Video copied; DTS or AC-3 audio becomes AAC | MKV to MP4 |
| MOV (iPhone, QuickTime) | Browser | H.264 and HEVC copied; ProRes re-encoded | MOV to MP4 |
| WebM | Browser | Re-encoded to H.264 + AAC for compatibility | WebM to MP4 |
| TS, M2TS | Browser | H.264 and HEVC copied | TS to MP4 |
| AVI (DivX, Xvid, MJPEG) | FFmpeg engine | Re-encoded to H.264 unless already H.264 | AVI to MP4 |
| WMV, ASF | FFmpeg engine | Re-encoded to H.264 + AAC | WMV to MP4 |
| FLV, F4V | FFmpeg engine | H.264 copied; Sorenson and VP6 re-encoded | FLV to MP4 |
| 3GP, 3G2 | Browser, FFmpeg for H.263 and AMR | H.263 and AMR become H.264 + AAC; H.264 is copied | 3GP to MP4 |
| HEVC video in any container | Browser, FFmpeg as fallback | Re-encoded to H.264 | HEVC to H.264 |
| MP4 going the other way | Browser | Copied into MOV, or re-encoded to VP9 WebM | MP4 to MOV · MP4 to WebM |
Can I convert a video to MP4 without losing quality?
Yes, whenever the video inside is already H.264, HEVC or AV1, which covers most phone, camera and download files. ProMedia then copies the compressed stream into the new container, a step called remuxing: every frame stays bit-for-bit identical, and even a long film finishes about as fast as your disk can read it.
Re-encoding happens only when the new format cannot hold the codec (ProRes cannot go into MP4), when you change resolution or frame rate, or when you switch on Always re-encode. The Quality preset then sets how many bits the encoder may spend.
| Preset | Browser encoder (WebCodecs) | FFmpeg engine (old formats) | Use it for |
|---|---|---|---|
| Faster | At most the source’s own bitrate, codec-adjusted | x264 at CRF 30 | Quick shares, smallest files |
| Balanced | At most 1.4× the source’s codec-adjusted bitrate | x264 at CRF 27 | Most conversions (default) |
| Best quality | At most 2× the source’s codec-adjusted bitrate | x264 at CRF 23 | Footage you will edit again |
Why a video file cannot be played
A video that will not open usually fails for one of three reasons. Each has a different fix, and only the first two are about format.
- The player does not know the container. MKV, WebM, AVI and FLV are the usual suspects on iPhones, TVs and in editors. Converting to MP4 fixes it, often in seconds.
- The player cannot decode the codec. An MP4 can still hold HEVC, which many Windows PCs and older TVs cannot decode without an add-on. Re-encode it with the HEVC to H.264 converter.
- The file is damaged. A recording that stops halfway, shows the wrong length or will not seek usually has a broken index. The repair video tool rebuilds the container and timestamps.
Why use this online video converter
- Nothing leaves your device. Conversion runs in the browser tab with WebCodecs and, for old formats, FFmpeg in WebAssembly. No server receives a copy of the file.
- No upload cap. The file is read from disk in pieces, so a long recording works on a desktop computer without waiting for an upload bar.
- Mixed batches. Drop an MKV, two MOVs and an AVI together. Each file converts in turn, and one failure does not stop the others.
- Offline after the first visit. The page and its engines are cached, so the converter keeps working on a plane or a locked-down network.
- No watermark, no account. The output is your video, changed only by the conversion you asked for.
Convert a video to MP4 on Windows, Mac, iPhone or Android
Any recent browser runs the converter. Only picking and saving files differs from device to device.
Windows 10 and 11
Open the page in Chrome, Edge or Firefox and drag files from File Explorer. Re-encodes use the graphics card where the browser allows. If a converted file still asks for HEVC Video Extensions, the codec is the problem, not the container.
Mac
Use Safari or Chrome. QuickTime Player’s Export As writes another MOV, so it cannot turn an MKV or AVI into MP4; this page can, and the MP4 opens in QuickTime, Photos and iMovie.
iPhone and iPad
In Safari, tap the drop zone and choose from Photos or Files. iPhone clips are MOV files with H.264 or HEVC inside, so MP4 output is a quick re-wrap. Save the result to Files or share it.
Android
In Chrome, tap the drop zone and pick files from your gallery or a file manager. Android cameras already record MP4; this converter is for MKV, AVI and other downloads the gallery will not play.
Tips & troubleshooting
Only need the sound? MP4 to MP3 or extract audio from video skip the picture and finish faster.
Converting does not make a remuxed file smaller. To fit an upload limit, use the video compressor and type the size you need.
Leave Resolution and Frame rate on Original for a lossless result. Changing either one forces a re-encode even when the codec could be copied.
Need exact codec, bitrate or keyframe control? Change video frame rate, codec and bitrate with the advanced encoder.
Renaming an extension is not converting: an .mkv renamed to .mp4 is still Matroska inside, and most players notice.
Video Converter FAQ
How do I convert a video to MP4 for free?
Drop the file on this page, keep MP4 selected and press Convert. The converter is free with no sign-up, watermark or daily limit, because the work runs on your own device rather than on a paid server.
Can I convert a video to MP4 without losing quality?
Yes, if the video is H.264, HEVC or AV1, which most files are. Those streams are copied into the MP4 unchanged. Each result card shows “copied (lossless)” or “re-encoded”, so you always know which one happened.
Why convert a video to MP4?
Because MP4 with H.264 and AAC is the combination phones, smart TVs, browsers, social apps and editing software all accept. Converting once saves everyone you send it to from hunting for a player that understands MKV, AVI or WebM.
Which video format is best?
For sharing and playback, MP4 with H.264 and AAC. For web pages aimed at modern browsers, WebM with VP9 or AV1 is smaller. MOV fits Apple editing workflows, and MKV is best for archiving files with several audio or subtitle tracks.
How do I convert a video to MP4 on iPhone or Android?
Open this page in Safari or Chrome, tap the drop zone and pick the video. The conversion runs on the phone itself. Copying streams needs little memory, but re-encoding a file of several gigabytes is more reliable on a computer.
Which formats can it open?
MP4, MOV, MKV, WebM and MPEG-TS are read by the browser. AVI, WMV, FLV, MPG and old 3GP codecs use the FFmpeg engine, which downloads once (about 31 MB) and is cached for offline use. Outputs are MP4, WebM, MOV and MKV.
Is there a file size limit?
There is no upload limit because there is no upload. Videos are read in chunks straight from disk, so multi-gigabyte files work on desktop computers; phones are limited by their memory. There are no daily caps and no watermark.